Ian Ott of SabresDigitalPressBox.com reported O'Reilly's seven-year extension with the Sabres.
Elliotte Friedman of Hockey Night in Canada reported that Buffalo will pay O'Reilly an average salary of $7.5 million for the duration of his contract, putting the total value of the deal around $52.5 million.
O'Reilly's deal with the Sabres comes one week after the team acquired him along with Jamie McGinn from Colorado in exchange for Nikita Zadorov, Mikhail Grigorenko, J.T. Compher and the 31st overall pick in the draft.
The 23-year-old O'Reilly has come into his own the last two seasons, recording 119 points and 12.3 points shares in 162 games over that span, per Hockey-Reference.com. He's also regarded as a great leader and teammate on the ice, as evidenced by being awarded the 2013-14 Lady Byng Memorial Trophy.
The Sabres have been trying to climb out of the NHL doldrums, missing the playoffs each of the last four years and finishing with a league-low 54 points last season. Pairing O'Reilly with incoming rookie Jack Eichel gives Buffalo two talented centers to build around.
Even though the rest of the roster may not be ready to keep up with Eichel and O'Reilly, the Sabres are on the right track and have two key pieces locked in long-term.
Read more Buffalo Sabres news on BleacherReport.com